Carpenters are often required to join pieces of material (i.e. wood, composites, etc.) at a corner. When joining the pieces of material, the contacting ends of the pieces must be mitered in order to match the angle of the corner and produce an aesthetically pleasing joint. The first step needed to create a proper corner joint is to measure the angle between the converging surfaces. Once the angle is known, the measured angle is bisected and the carpenter's mitering tools are set to the value of the bisected angle. Both converging pieces of material are then cut to the bisected angle. When joined, the pieces of material meet at an angle equal to the measured angle, creating a proper corner joint.
When corners meet at a right (90°) angle, the mitering process is relatively simple. Corners that require miter joints, however, are rarely a perfect right angle. A nominal ‘right angle’ can, in practice, vary by several degrees on either side of the accepted right angle. When pieces of material must be joined at an acute or obtuse angle, the task of creating a proper corner joint becomes much more complex. For example, a pair of walls may converge at 88.5° at a ceiling, 90.3° midway between ceiling and floor, and 91.6° at the floor. These varying angles must be accurately and quickly measured, and the measurement must then be accurately and quickly transferred to a mitering tool (such as a miter saw).
Traditionally, mitered joints are created using a mitering tool such as a miter saw (also called a chop saw or drop saw). A miter saw makes cuts by pulling or pivoting a spinning circular saw blade down onto a workpiece of material in a short, controlled, chopping motion. The workpiece is typically held against a fence, which provides a standard cutting angle between the blade and the longest workpiece edge. Typically, the standard cutting angle of the fence is fixed at 90°. A primary feature of a miter saw is the miter index, which allows the angle of the saw blade to be changed relative to the fence (i.e., the blade can be rotated left to right to set it at an angle with respect to the fence). While many miter saws enable one-degree incremental changes to the miter index, many also provide “stops” that allow the miter index to be quickly set to common angles (such as 15°, 30°, or 45°). A compound feature (i.e., a compound miter saw) further allows the angle of the cutting blade to be changed relative to the horizontal plane. Thus, the blade can be angled left or right (called the miter angle); in addition, the blade can be tilted side to side (called the bevel angle), which allows the saw to be used for bevel cutting. Most compound features allow the angle to be set between 0° and 50°, while a less-common “double-bevel” allows the angle to be set between −50° and 50°.
While current miter saws provide an effective means to create miter edge, they are prone to inaccurate measurements. Using the scale on a miter saw to cut miters for imperfect angles can result in poorly fitting corner joints on door frames, window trim, and all types of moldings. This is especially important for large crown moldings, where a small error in angle could translate into a large visible gap between two pieces of material. A miter saw, furthermore, requires a user to take a direct measurement of an angle using, e.g., a protractor or other angle gauge, and then to correlate that measurement with the miter index of the saw, manually adjusting the position of the blade with respect to the fence (and thus the workpiece). Thus, the angle of the crosscut is an indirect measurement, which is prone to inaccurate transfer to the miter saw.
An angle gauge may also be used to transfer the measured angle directly to the workpiece. While the angle defined by the conjoined walls will be accurately captured, error may be introduced when the measurement is transferred to the workpiece. For example, the measurement is transferred by marking the board to be cut with a pencil, and then the cut must be made along the pencil line. The pencil line itself may not accurately reflect the true position of the rules, and the cut along said line may introduce still further error because the operator of the miter saw must visually guide the saw along the pencil line. Errors may result from other sources including making incorrect measurements, incorrectly setting the miter index value, or from differences in scale between the measuring and cutting devices.
Consequently, it is desirable to provide a system wherein the crosscut made into a workpiece is a direct measurement of the corresponding corner. It is further desirable to provide a system that eliminates the step of transferring a measured angle to a workpiece, as well as the step of requiring a craftsman to cut carefully along said angle. A system is also needed that eliminates the step of reading a miter angle setting from a tool and setting the miter saw to the setting.